Composite sliding member

ABSTRACT

In a preferred embodiment a sliding member, such as an apex seal in a rotary internal combustion engine, is formed of particulate carbon interdispersed with, and metallurgically bonded to, a copper base alloy containing, by weight, 3% to 22% lead,, and titanium and optionally tin in amounts providing effective wetting and bonding of the metallic phase to the carbon and yet not substantially detracting from the physical strength of the composite, the carbon phase making up 20% to 80% by volume of the composite seal member. In various sliding members that have been evaluated as apex seals 5% to 20% of titanium and up to 15% tin in the copper base alloy have been successfully employed. Seal members of this composition are wear resistant and can be employed to particular advantage in combination with a rotor housing having a hard chrome wear surface.

United States Patent [191 Lindsey 1 Mar. 4, 1975 1 1 COMPOSITE SLIDINGMEMBER David M. Lindsey, Taylor, Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: May 2, 1973 [21] Appl. No.: 356,611

[75] Inventor:

[52] U.S. Cl 29/I82.8, 75/156, 75/163, 75/164 [51] Int. Cl. C22c 1/04[58] Field of Search 75/156, 163, 164; 29/1825, 182.8; 418/179 [56]References Cited UNITED STATES PATENTS 3,114,197 12/1963 Du Bois 29/1825X 3,177,564 4/1965 Reynolds et al.. 29/1825 3.191.278 6/1965 Kendall eta1 29/182 5 3,545,901 12/1970 Belzner 418/179 3,782,930 l/1974 Shibata29/1828 X 3.795.493 3/1974 Merth 29/1825 Primary E.\'aminerL. DewayneRutledge Assistant E.raminerArthur J. Steiner Attorney, Agent, orFirnzGeorge A. Grove [57] ABSTRACT In a preferred embodiment a slidingmember, such as an apex seal in a rotary internal combustion engine, isformed of particulate carbon interdispersed with, and metallurgicallybonded to, a copper base alloy containing, by weight, 3% to 22% lead.,and titanium and optionally tin in amounts providing effective wettingand bonding of the metallic phase to the carbon and yet notsubstantially detracting from the physical strength of the composite,the carbon phase making up 20% to 80% by volume of the composite sealmember. In various sliding members that have been evaluated as apexseals 5% to 20% of titanium and up to 15% tin in the copper base alloyhave been successfully employed. Seal members of this composition arewear resistant and can be employed to particular advantage incombination with a rotor housing having a hard chrome wear surface.

4 Claims, 3 Drawing Figures PMENTEUHAR 413.;

till-ill!!! COMPOSITE SLIDING MEMBER This invention relates tometal-carbon composite compositions for use in forming sliding machineelements such as seals. More particularly, this invention relates totitanium-containing, copper base alloycarbon compositions suitable forforming rotary internal combustion engine apex seals.

Rotary mechanisms, such as internal combustion engines, pumps andcompressors, are known and now being developed for many differentapplications. In general, such rotary mechanisms comprise an outerperipheral wall body, interconnected by a pair of parallel end walls todefine a cavity whose peripheral shape is basically an epitrochoid. Arotatably mounted rotor is supported on a shaft within the cavity. Theouter surface of the rotor defines a plurality of circumferentiallyspaced apex portions having radially movable seal strips mounted thereinfor sealing engagement with the inner surface of the peripheral wall.Thus, working chambers are formed between the rotor and peripheral wallwhich vary in volume upon relative rotation of the rotor and the outerbody. An intake port is provided which, in the case of an internalcombustion engine, admits air or an air-fuel mixture for supplying thecombustion zone of the engine. An exhaust port is provided for expellingthe working fluid, such as the burnt gases in the case of the engine. Inan engine ignition means may be provided for ignition of the fuel-airmixture so that the stages of intake, compression, expansion and exhaustmay be carried out.

In the successful operation of a rotary mechanism of the type describedthere must be effective sealing contact between the apex seal strips andthe inner surface of the peripheral wall over the useful life of themechanism. In fact, the level of performance of the mechanism dependsupon there being minimal or no leakage between a seal and the peripheralsurface so that the several working chambers are effectively isolatedfrom each other. In the case of the rotary engine many differentmaterials have been evaluated for the manufacture of the apex seals andthe peripheral rotor housing. For example, a rotor housing constructionthat has been used commercially is formed of an aluminum alloy. Thealuminum alloy is employed because of its relatively low weight and highthermal conductivity. An intermediate layer of iron is formed on theinner peripheral surface of the light alloy housing. Iron bonds wellwith the aluminum alloy and provides a relatively harder surface. Thisintermediate layer is relatively thin, typically about 0.025 inch to0.050 inch so that it will not be subject to large thermal stresses.After the bonding of the iron layer to the housing, a relatively thininner layer of hard chrome is applied, typically by electroplating. Thechrome layer is the wear surface of the peripheral housing against whichthe apex seals slide.

Various mixtures of materials have been proposed for the manufacture ofapex seals, including those which are intended to run against a hardchrome surface. For example, various types of carbon and mixtures ofcarbon with tin, lead, zinc, antimony and aluminum have been considered.Of these, at least the aluminum alloy-carbon seals have been employedcommercially. Examples of such seal materials are described in BritishPat. No. 1,234,634 and German Offenlegungsschrift No. 2,034,896. Thealuminumcarbon seals have been used in relatively small (120 in.

and 14 0 in. swept volume 2 rotors) or low performance rotary engines.However, they have been found to fail in larger engines (e.g., 200 in.and 266 in. swept volume 2 rotors) where the seal strip must be longerand subject to more flexing, and in higher performance engines where theseal is subjected to more severe loads and temperatures.

For optimum results in a rotary mechanism it is recognized that thematerial of the apex seal and the wear surface of the peripheral housingmust both be considered and selected so that they operate well together.For example, a very hard seal material may be chosen which resists sealwear but produces excessive wear of the housing. Conversely, hardhousing surfaces may be chosen which produce excessive :seal wear orfailure.

It is an object of the present invention to provide a sliding memberhaving particular utility as an apex seal member in a rotary internalcombustion engine. The sliding member is a composite of carbon particlesdispersed in a copper base alloy matrix. The copper base alloy ischaracterized by the presence of titanium, lead and optionally tin. Thecomposition is especially advantageous as a rotary engine apex sealmember characterized by strength at high engine temperatures and/or inlarger engines, and minimal wear of both the seal itself and the housingagainst which it slides.

In accordance with a preferred embodiment of my invention, these andother objects are accomplished by providing a composite sliding elementor sea] member which is characterized by the presence of small carbonparticles interdispersed in a suitable copper base alloy. The copperbase alloy contains, by weight, 5% to 20% titanium, 3% to 22% lead and0% to 15% tin. A particularly preferred copper base alloy for use inthis composite composition in rotary engine apex seals consistsessentially, by weight, of 9% to 18% titanium, 4% to 10% lead, 4% to 13%tin and the balance copper excluding impurities. Since this copper basealloy contains both titanium and lead in significant amounts it may begenerally characterized as a titanium bronze. The compositecarbon-titanium bronze sliding members of my invention may be preparedby any of a number of known techniques which will be described such thatthe carbon particles and copper alloy are generally uniformlyinterdispersed and there is a metallurgical bond at the interface of thecarbon particles and the metallic phase. The carbon may make up 20% toby volume of the subject seal composition, but preferably thecomposition consists of 40% to 65% by volume carbon and the balancemetal phase. The composition of my invention provides high flexuralstrength even at temperatures as high as 900 F. It is chemically stablein the hot water containing environment of an internal combustionengine. The copper base alloy employed in accordance with my inventionprovides good wetting of the particulate carbon phase, resulting inhigher strength seals and yet requires less expensive manufacturingtechniques because of the improved wetting.

These and other objects and advantages of my invention will become moreapparent from a detailed description thereof which follows. In thedescription reference will be had to the drawings, in which:

FIG. 1 is an elevational view partly in section of the rotor housing androtor assembly of a rotary engine;

FIG. 2 depicts a rotary engine apex seal; and

FIG. 3 is a photomicrograph at 200X magnification showing themicrostructure of a composite seal composition of my invention.

With reference to FIG. 1, there is shown a side view partly in sectionof the rotor assembly and peripheral housing of a rotary engine. Therotary combustion engine comprises a stationary outer body formed by aperipheral wall or rotor housing 12. The rotor housing is interconnectedwith end housings 14 (only one shown) to form a rotor cavity 16. Asviewed in FIG. I the inner surface 13 of the peripheral wall 12 has amultilobed (two-lobe) profile which is basically a twolobed epitrochoidor a curve parallel thereto whose center is indicated at 20. Acrankshaft 22 is rotatably supported within the end housings 14 bybearing means, not shown, so that the shaft axis is coincident with aline through the center 20 parallel to the peripheral wall 12. Thecrankshaft 22 has an eccentric 24 in the rotor cavity 16. Rotatablysupported on the eccentric 24 is a rotor 26 having threecircumferentially spaced apex portions 28, in each of which there is aspring biased, radially movable apex seal strip 30. Each seal strip 30(see also FIG. 2) extends completely across the rotor cavity 16 from oneend housing 14-to the opposite one.

An annular externally toothed gear 32 is received about and isconcentric with the crankshaft 22 and is rigidly secured to an enginehousing 14. The gear 32 meshes with an internally toothed gear 34 thatis concentric with and fixed to one side of the rotor 26. The gear 34has one and one-half times the number of teeth as the gear 32, with theresult that this gearing enforces a fixed cyclic relation between therotor and the crankshaft such that the crankshaft, which is the enginesoutput shaft, makes three complete revolutions for every one completerevolution of the rotor. The rotor faces 36 cooperate with theperipheral wall 12 and with the side walls 14 to define three variablevolume working chambers 44 that are spaced around and move with therotor within the housing as the rotor orbits within the rotor cavity.

Side seals 38 are provided within each of the side faces 40 of the rotorfor sealing engagement with the inner surfaces of the end housings.These seals mate with corner seal bodies 42 which also aid in supportingthe apex seal strips 30 in each of the apex portions. Thus, a continuousseal is provided for each of the working chambers 44 defined between thefaces 36 and apex portions 28 of the rotor and inner surface 13 of theperipheral wall 12. As the rotor and outer body rotate relative to oneanother, the working chambers being defined between the apex portions ofthe rotor and the inner surface of the peripheral wall vary in volume asis known.

As depicted in FIG. I, an intake port 46 is provided in end housing 14for admitting air or a fuel-air mixture to supply the combustion zone ofthe engine. An exhaust port 48 is provided in the peripheral wall 12 forexpelling the combustion products. An ignition means 50 may be providedfor ignition of the fuel-air mixture. It may be eliminated if the engineis run on a diesel cycle.

In accordance with a preferred application of the apex seal memberembodiment'of my invention the rotor housing 12 is preferably formedfrom a lightweight alloy material (indicated at 52), such as aluminum,aluminum alloy, magnesium or magnesium alloy,

and the inner surface 13 of the peripheral wall is provided with a liner54 to increase the wear life of the inner surface and of the apex sealstrips. The light alloy housing has an intermediate layer 56 bonded toits 5 inner surface which may be formed of molybdenum, iron or steel, ora combination thereof. These materials bond well with the light alloyhousing and provide a relatively hard surface. As is now known, theintermediate layer may be formed by a known transplant casting method.In accordance with this method, a mandrel is designed so that its outersurface substantially defines the shape of the housing cavity. Asuitable parting compound is applied to the surface of the mandrel andthe material of the intermediate layer is sprayed onto the mandrel in alayer 0.025 inch to 0.050 inch in thickness. The light alloy housing isthen cast around the preformed intermediate layer and the mandrel isremoved, leaving the intermediate layer 56 securely bonded to thehousing.

After bonding of the intermediate layer 56 to the housing 12 arelatively thin layer 58 of high wear resistant metal, preferablychromium or chromium alloy, is deposited onto the intermediate layer toform a hard, smooth, wear resistant, relatively low friction surface forengagement by the apex seal strips. The chromium layer may beelectrodeposited onto the intermediate layer. The chromium layer 58after finish grinding is quite thin, typically 0.002 inch to 0.010 inchin thickness.

The subject apex seals (depicted at 30 in FIGS. 1 and- 2) have also beenemployed with a cast iron rotor housing having a chrome plated innersurface.

The seals and other sliding members of my invention are formed of ametal-carbon composite which is durable and wear resistant, e.g., underthe dynamic conditions experienced in the apex position of the Wankeltype rotary engines. In a preferred embodiment a composite apex sealconsists of finely divided, particulate carbon dispersed 'in andmetallurgically bonded to a continuous interconnecting phase of acopper-titanium alloy containing some lead. The metal portion and thecarbon portion of the seal complement each other insofar as wear,strength and frictional characteristics are concerned. It is believedthat a significant factor in the performance of my seal composition isthe bonding of the titanium bronze alloy to the carbon due to wettingenhanced by the lead and the formation of interfacial titanium carbides.chromplated,

The titanium bronze alloy used in my sliding member compositionscontains, by weight, 3% to 22% lead, optionally up to about 15% tin,titanium in an amount providing effective wetting and bonding of themetal phase to the carbon without substantially detracting from thestrength and toughness of the composite, and the balance copper. Asindicated above, I employ titanium and lead to cause the copper basealloy to wet the carbon particles. I prefer to employ at least about 5%by weight titanium in the copper base alloy. A titanium content inexcess of 20% by weight of the alloy does not appear to furthercontribute to the useful strength of my composite and can causedetrimental embrittlement. Lead contents in excess of 22% by weight ofthe alloy may unduly soften the composite seal. Tin contributes to thedesirable friction properties of the composite seal. Preferably, thealloy portion of my composite seal consists essentially, by weight, of9% to l8% titanium, 4% to 13% lead, 4% to tin and the balance copperexcluding impurities.

Sliding members of the subject composition may be formed by theemployment of standard power metallurgy processes. When such techniquesare employed the carbon and copper base alloys, of course, must be infinely divided, particulate form. The carbonaceous particles employed inaccordance with the invention are hard, wear resistant grades of carbon(amorphous or crystalline), such as anthracite coal, vitreous carbon andsynthetic carbons containing crystalline carbon. In an apex sealapplication amorphous carbon-graphite mixtures (containing up to 15% tographite) may also be employed, but graphite alone is too soft. In lessstringent wear situations graphite alone may be used as the carbonconstituent.

The carbon is preferably 325 mesh size although somewhat largerparticles (200+325 mesh) have been used. I have found, however, thatpitting of the composite is more likely to occur in apex sealapplications if the carbon mesh size is larger than 3 mesh. Carbonparticles of 325 mesh size are prepared by known comminuting procedures,such as ball or rod milling. In the subject metal-carbon composites 20to 80 volume percent of carbon is present. The subject titanium bronzealloy may be prepared in particulate form by atomizing molten alloy inan argon atmosphere. A 325 mesh alloy powder of high purity is thusformed. It is not necessary to use prealloyed powder. A powder mixtureof the individual constituents can suitably be employed.

Carbon powder 325 mesh and copper base alloy powder 325 mesh aremeasured out by weight or by volume in the desired proportions. They arethoroughly blended together by standard blending techniques andequipment. The powder blend is then consolidated into a unitarycomposite member.

One technique of accomplishing this is by vacuum hot pressing. Thepowder blend is placed in a carbon die of suitable predeterminedconfiguration. Individual seal members can be formed, or a large blockof composite material may be formed from which seals are cut ormachined. Pressure is applied through the carbon dies to the powderblend in an apparatus arranged and constructed so that all air can beevacuated from around the powder mixture and replaced with argon orother suitable inert gas. A pressure of 1,000 psi is maintained on thepowder as it is heated from room temperature to l,800 F. The pressure isthen increased to 6,000 psi while the l,800 F. temperature is maintainedfor minutes. The composite material is then permitted to cool to roomtemperature, the pressure being relieved when the temperature has fallenbelow about l,400 F. Under the high temperature and pressure conditionsthe copper base alloy melts and wets the carbon particles forming aninterfacial metallurgical bond therewith. The wetting is enhanced by thepressure of the lead and titanium, and titanium carbide is formed.

As seen in FIG. 3, the microstructure (shown at 200X) consists of carbonparticles 60, each surrounded by the copper alloy metallic phase 62. Thecopper phase is strengthened by the presence of tin and titanium. Thelead is present as discrete particles, randomly distributed in themetallic phase (not visible at 200X). There is a metallurgical bondbetween the metallic phase and the carbon. Titanium from the metallicphase reacts with the carbon to form titanium carbide. Evidence for thisis seen in an X-ray diffraction pattern and in an electron microprobeanalysis for titanium. This carbide provides the bond between themetallic matrix and the carbon particle.

The carbon-titanium bronze mixture may also be consolidated into mycomposite seal member by other known powder metallurgical techniques,such as isostatic hot pressing (wherein the powder mixture is placed ina glass or metal can and subjected to high fluid pressure); atmospherichot pressing (using additives such as titanium hydride which decomposeto provide a protective atmosphere); cold pressing and sintering; coldpressing, presinter and hot forming; or extrusion.

My composite seal members may also be formed by a warm forming methodutilizing an inert atmosphere. A suitable mixture of 325 mesh titaniumbronze alloy and carbon powders (for example, 5050 by volume) are purgedwith argon and heated in an argon atmosphere to l,800 F. In themeantime, forging dies having a cavity adapted to receive the hot powdermixture are heated to 500 F. Preheated powder is placed in the die and apressure of twenty tons per square inch imposed for about a minute. Thepressure is released and a formed composite block is removed from thedie. Individual seal members, such as that depicted in FIG. 2, aremachined from the block.

In order that a finished seal will better hold its dimensions whenexperiencing the elevated temperatures of a rotary engine, the blockfrom which individual seals A few specific examples will furtherillustrate my in- I vention. A 325 mesh prealloyed powder (designatedAM-l consisting essentially, by weight, of 9.9% titanium, 9.1% lead,9.2% tin and the balance copper, was obtained. This metal alloy powderwas thoroughly mixed with 325 mesh anthracite coal powder. The amorphouscarbon powder made up 20% by weight of the mixture. The mixture was hotpressed in a vacuum to form a composite block consisting ofapproximately equal proportions by volume of carbon particles and copperbase alloy matrix. Apex seals were machined from the blanks and placedin a commercial rotary combustion engine. The epitrochoidal housing ofthe engine had a hard chrome surface against which the subject sealsran. The engine was run driving a dynamometer for hours. At the end ofthat time the engine was dismantled and the seals examined. The averageWear of the three seals (from one rotor) was found to be 6.5 mils duringthe 100 hours. In a companion test of seals formed of the above alloy,but a different carbon (U.S. Graphite Co. Graphitar 34), in a similarengine the average seal wear was found to be 2.9 mils over the 100 hourtest. These seals were considered to have operated in a whollysatisfactory manner.

For purposes of comparison, commercial aluminum alloy-carbon compositeseals of the type described above were also run in commercial rotaryengines of the same design as those employed in the abovedescribedtests. In two different dynamometer runs identical to those employedabove the average wear of the aluminum-carbon composite seals was foundto be 9.3 mils per 100 hours and 7.4 mils per 100 hours, respectively.

Another set of composite apex seal members were prepared as describedabove in accordance with my invention, except that in this instance thecopper base alloy (designated J) consisted essentially, by weight, of16.3% titanium, 8.8% lead, 7.7% tin and the balance copper. Furthermore,a quantity of amorphous carbon particles was employed such that thecarbon made up about 65% by volume of the composite seal member. Asabove, the carbon particles were initially 325 mesh. A set of theseseals was also tested in a commercial rotary internal combustion enginedriving a dynamometer over a 100 hour test. The average wear of theseals was 8.9 mils. These seals also were considered to have performedsatisfactorily; A'number of other carbon-titanium bronze alloy compositeseals have been produced and tested in commercial rotary engines asdescribed above. in each instance an essentially amorphous 325 meshcarbon was employed in amounts such as to make up 50% to 65% by volumeof the alloy.

engine, more or less of the type described having hard chromeplated,layered rotor housings. A number ofthe seals were also placed in a 120in. swept volume engine, also of the general type described having ahard chrome plated layer on the rotor housing. Purchased prior artaluminum-carbon seals were placed in both a 206 in. engine and a l20 in.engine. Titanium bronzecarbon seals of the above composition, but formedby the warm forming process described above, were also placed in a 206in. engine and a 120 in. engine. All of the 206 in. engines containingthe respective seal members were operated steadily for a prolongedperiod of time under the same predetermined engine durability schedule.The 120 in. enginescontaining the same respective seals were likewisesteadily operated for a prolonged period of time but under a differentdurability schedule. At the end of the tests the engines weredisassembled and all of the seals examined. The wear rate and otherproperties for the various seals in the re- Finely divided, prealloyed,titanium bronze powders 2O spective engines were as follows:

206 in. Engine 120 in. Engine Seal How Wear Rate Wear Rate PittingModulus of Rupture (PSI) Material Obtained (Mils/lOO hrs.) (Mils/l00hrs.) Resistance 75 F. 700 F. 900 F.

Aluminum- Carbon Purchased 13.0 3.0 Fair 38,400 28,200 21,000 TitaniumVacuum Bronze- Hot Carbon Pressing 5.5 2.0 Good 43,200 37, I00 31,000Titanium Bronze- Warm v Carbon Forming 8.5 1.5 Good 44,800 38,000 32,000

were employed having compositions as tabulated below.

Composite apex seals, wherein the above alloys were employed as themetal phase, all were tested in commercial engines and found to operategenerally satisfactorily. It was felt, however, that the alloydesignated AM-2" was probably at about the upper limit for suitable leadcontent since the wear of these seals was relatively higher than otherseals in accordance with this invention and some lead was observed tohave sweated out of the composite during heat treatment at 850 F.

In another example of the performance of a composite seal member inaccordance with my invention, a titanium bronze alloy powder (325 mesh)of the following composition, by weight, was obtained: 71% copper,titanium, 4.5% lead and 9.5% tin. Anthracite coal powder (325 mesh) wasalso obtained and a powder blend of the alloy and carbon consisting ofby weight calcined anthracite and 80% by weight titanium bronze alloywas prepared. This powder blend was consolidated into a number of apexseal members, such as depicted in FIG. 2, by the vacuum hot pressingtechnique described above. This mixture resulted in a composite sealwhich consisted of about 50% metallic phase and 50% anthracite byvolume. These seals were placed in a 206 in. swept volume rotarycombustion It is seen that the wear rates for the sliding members of myinvention are lower than for the most directly comparable known priorart seals. In addition, the modulus of rupture of my sliding members issignificantly greater both at room temperature and at temperatures of700 F. and 900 F.

It is recognized that, in general, metal alloy-carbon composites may beformed more or less in accordance with the procedure outlined in Hucke,US. Pat. Nos. 3,235,346 and 3,348,967. In accordance with Hucke apermeable framework of carbon is provided and the framework isinfiltrated with a suitable molten metal alloy. Depending upon thecomposition of the infiltrating alloy, the conditions under whichinfiltration is accomplished, or subsequent conditions, the alloy may ormay not form a metallurgical bond with the continuous framework ofcarbon. However, structures produced in this manner have thus farexperienced substantial chipping when employed as apex seal members inrotary engines. Chipping from the surface of the seal member in such anapplication is, of course, undesirable because the effectiveness of theseal is thereby diminished and engine performance decreases. Thestructure of the present invention differs from Hucke as a result of theuse of a particulate mixture of carbon and the copper base alloy, thecomposition of the alloy and in the avoidance of such chipping due tothe coaction of all of the initially particulate ingredients.

While my invention has been described in terms of some preferredembodiments thereof, it will be appreciated that other forms thereofcould readily be adapted by one skilled in the art. Accordingly, it isto be understood that the scope of my invention is to be limited only bythe following claims.

What is claimed is:

l. A liquid phase sintered metal-carbon composite sliding member formedof carbon uniformly dispersed in and metallurgically bonded to a phaseof a copper base alloy, said copper base alloy consisting essentially,by weight, of 5% to 20% titanium, 3% to 22% lead, to 15% tin and thebalance copper, said carbon making up about 20% to 80% by volume of saidcomposite member, said metallurgical bond comprising titanium carbide.

2. A liquid phase sintered metal-carbon composite sliding memberconsisting essentially of particulate carbon dispersed in andmetallurgically bonded to a continuous interconnecting phase of a copperbase alloy, said carbon particles being initially about 200 mesh orsmaller and collectively making up 20 to 80 volume percent of saidcomposite member, said copper base alloy consisting essentially, byweight, of to 20% titanium, 3% to 22% lead, 0% to tin and the balancecopper, said metallurgical bond comprising titanium carbide.

3. A liquid phase sintered metal-carbon composite sliding memberparticularly suitable for use as a rotary engine apex seal memberconsisting essentially of particulate carbon dispersed in andmetallurgically bonded to a continuous interconnecting phase of a copperbase alloy, said carbon particles being initially 325 mesh andcollectively making up about 40 to 65 volume percent of said compositemember, said copper base alloy consisting essentially, by weight, of 5%to 20% titanium, 3% to 22% lead, 4% to 15% tin and the balance copper,said metallurgical bond comprising titanium carbide.

4. A liquid phase sintered metal-carbon composite sliding memberparticularly suitable for use as a rotary engine apex seal member formedof carbon particles dispersed in and metallurgically bonded to aninterconnecting phase of a copper base alloy, said carbon particlesbeing initially --325 mesh and collectively making up about 40 to 65volume percent of said composite member, said copper base alloyconsisting essentially, by weight, of 9% to 18% titanium, 4% to 10%lead, 4% to 13% tin and the balance copper, said metallurgical bondcomprising titanium carbide.

1. A LIQUID PHASE SINTERED METAL-CARBON COMPOSITE SLIDING MEMBER FORMEDOF CARBON UNIFORMLY DISPERSED IN AND METALLURGICALLY BONDED TO A PHASEOF A COPPER BASE ALLOY, SAID COPPER BASE ALLOY CONSISTING ESSENTIALLY ,BY WEIGHT, OF 5% TO 20% TITAIUM, 3% TO 22% LEAD, 0% TO 15% TIN AND THEBALANCE COPPER, SAID CARBON MAKING UP ABOUT 20% TO 80% BY VOLUME OF SAIDCOMPOSITE MEMBER, SAID METALLURGICAL BOND COMPRISING TITANIUM CARBIDE.2. A liquid phase sintered metal-carbon composite sliding memberconsisting essentially of particulate carbon dispersed in andmetallurgically bonded to a continuous interconnecting phase of a copperbase alloy, said carbon particles being initially about 200 mesh orsmaller and collectively making up 20 to 80 volume percent of saidcomposite member, said copper base alloy consisting essentially, byweight, of 5% to 20% titanium, 3% to 22% lead, 0% to 15% tin and thebalance copper, said metallurgical bond comprising titanium carbide. 3.A liquid phase sintered metal-carbon composite sliding memberparticularly suitable for use as a rotary engine apex seal memberconsisting essentially of particulate carbon dispersed in andmetallurgically bonded to a continuous interconnecting phase of a copperbase alloy, said carbon particles being initially -325 mesh andcollectively making up about 40 to 65 volume percent of said compositemember, said copper base alloy consisting essentially, by weight, of 5%to 20% titanium, 3% to 22% lead, 4% to 15% tin and the balance copper,said metallurgical bond comprising titanium carbide.
 4. A liquid phasesintered metal-carbon composite sliding member particularly suitable foruse as a rotary engine apex seal member formed of carbon particlesdispersed in and metallurgically bonded to an interconnecting phase of acopper base alloy, said carbon particles being initially -325 mesh andcollectively making up about 40 to 65 volume percent of said compositemember, said copper base alloy consisting essentially, by weight, of 9%to 18% titanium, 4% to 10% lead, 4% to 13% tin and the balance copper,said metallurgical bond comprising titanium carbide.